1. Field of the Invention
The present invention relates to a method and an apparatus for indexing a moving portion of a robot to a mechanical orgin.
2. Description of the Prior Art
In the prior art, there is known a robot which is constructed to include a base, a first arm having its one end borne in a swinging manner by the base, and a second arm having its one end borne in a swinging manner by the other end of the first arm. This robot is driven to operate by a servomotor which in turn is controlled by a control unit.
In order to control the motions of the robot accurately, the individual arms have their reference positions stored as mechanical origins so that they have to be indexed to the mechanical origins before the storage. Japanese Utility Model Laid-Open No. 171095/1984 has disclosed an origin indexing apparatus of plug gauge type. According to this disclosure, adjacent arms are formed with holes or grooves for determining their positional relations so that the origins are indexed by inserting a rod-shaped plug gauge closely into those holes or grooves. Specifically, the worker moves the arms to align the holes or grooves formed therein and then inserts the plug gauge into the holes or grooves.
In order to enhance the accuracy in the origin indexing, however, the gaps between the holes or grooves and the plug gauge has to be minimized. Thus, it is difficult to position the holes or grooves of the arms in alignment thereby to allow the plug gauge to be inserted thereinto.